The present disclosure relates to hand gauges for measuring material thickness and more particularly to such a hand operated gauge capable of more precise measurements and particularly a hand operated thickness measuring gauge capable of avoiding error due to the differences in applied hand pressure of different operators.
Contact measuring tools are widely used to measure the thickness of flat materials by utilizing a linear gauge or the like. When measurements involve simultaneously contacting opposing sides of material (specimen) and determining the thickness thereof, conventional tools are used such as are described in US patents: U.S. Pat. Nos. 202,866; 346,706; 2,051,357; 2,080,534; 2,152,880; 2,734,275; and 3,208,148. In common use are gauges that use a C-shaped jaw having a fixed jaw opening and which have a fixed handle mounted as a part of the jaw, and a pivoting handle also mounted to the jaw allowing the two handles to be squeezed toward each other thereby drawing a fixed and a movable surface contactors toward each other. The stationary contactor is secured to one side of the jaw, while the movable contactor is mounted on a probe of a measurement gauge which is mounted on the opposing side of the jaw, with the two contactors facing each other. The pivoting handle is engaged with the probe so that by drawing the handles toward each other, the two contactors may be brought into mutual contact for zeroing the measurement gauge, and also into contact with opposing sides of the material (specimen) placed between the contacts so as to measure its thickness as indicated by the measurement gauge. Of course the measurement gauge may be read directly, or may be fitted for transmitting a measurement to a distant recorder. Such a hand tool provides significant convenience when thickness measurements must be made directly on a large work piece as for instance in an assembly area.
The accuracy of measurement is influenced, for example, by the pressure applied by the operator, the rigidity of the tool in general, by the flatness and parallelism of the opposing contacts, and by any warp in the specimen. The measuring accuracy is affected as well by distortion of the specimen caused by the contacts. The advantages of a hand tool, include portability, measurement speed, and adaptability to the measurement situation, i.e., the ability to place the tool into various attitudes and positions to accommodate the location and position of the specimen. Clearly, the use of such a tool has disadvantages as well. For example accuracy may suffer due to changes in ambient temperature within a factory site over the course of a work shift. Dust particles may degrade both accuracy and precision. The tool may suffer contact or gauge misalignment due to rough handling. Of course by proper operator training and ambient conditions control, these problems can be minimized. Error may also be caused by variations in the hand force applied to the handles during a measurement. Such force variations can change the linear dimension of the jaw's opening. For instance, a common micrometer holds a measurement gauge at one jaw of the tool. A workpiece is inserted between its jaws and the gauge probe is moved in contact with the workpiece. The force of the probe exerts a force against the workpiece and also against the lower jaw. This force tends to cause strain between the jaws which introduces measurement error. The presently described tool avoids this source of error as will be described thereby providing improved measurement accuracy and precision.